1. Field of the Invention
The present invention generally relates to methods and apparatus for containing and controlling waste during the cleaning of surfaces. The methods and apparatus of the present invention are particularly useful for cleaning industrial and commercial surfaces, e.g., concrete and asphalt slabs and steel surfaces such as tanks and ship hulls, which have become contaminated with oil, grease and other chemicals. More specifically, the present invention is directed to methods and apparatus which employ a unique application of a vacuum to the surface being cleaned to allow complete control of dislodged contaminants, e.g., heavy metals, radioactive materials, PCBs (polychlorinated biphenyls) and other hazardous chemicals.
2. Description of the Background
The requirement for maintaining clean work areas in industrial and commercial environments is not only necessary for the maintenance of a healthy workplace but is also important in order to prevent contamination of the environment with trace chemicals dislodged in the cleaning process. As environmental standards are strengthened, the necessity for efficiently removing debris and contamination, including oil, grease, chemicals and the like, from hard surfaces in industrial and commercial settings is increasing. Once removed from the surface, it is also necessary to contain and transport the contaminants to an appropriate treatment facility.
Many commercially used cleaning processes employ vacuum and high velocity water streams to dislodge and remove contaminants. The contaminants are typically collected with the cleaning water in a vacuum truck for temporary storage and transport to a waste treatment facility. However, those processes are so inefficient due to inadequate containment and leakage that some of the dislodged material, including hazardous contaminants, are scattered to surrounding areas by the high velocity water streams. These scattered contaminants cause contamination of previously safe areas.
A common form of manually operated cleaning device for cleaning hard surfaces has come to be known in the industry as a slab cleaner. A typical slab cleaner has the general appearance of a lawnmower. However, a rotating arm for delivery of a high pressure water spray has been substituted for the cutting blade. Many attempts have been made to connect a vacuum source to such a device to direct air over the surface in order to entrain and remove water and dislodged contaminants. In the typical prior art device, a vacuum source was connected through the single wall housing of the slab cleaner. In order to maintain adequate airflow within the housing, a flexible skirt or lip was disposed about the periphery of the housing extending downward to the surface to be cleaned. Air could flow under this skirt and into the housing.
While the foregoing arrangement was typical of most prior art slab cleaning devices, it suffered from many deficiencies. In general, there was little or no means for controlling the airflow within the housing and across the surface being cleaned. Because the vacuum acted on the total surface area covered by the housing, these prior art devices had a tendency, in some circumstances, to suck down on the surface with so much force that it was impossible to maneuver the device across the surface. In those circumstances, the cleaning operation had to be stopped and the vacuum released before cleaning could resume. If, however, the gap around the periphery of the housing was increased to prevent vacuum suck down, the additional space could allow escape of the high pressure water stream and dislodged contaminants. Airflow around the perimeter was controlled by the size of the gap between the housing and surface being cleaned. Therefore, elevation changes around the perimeter and surface deformities, e.g., expansion joints and uneven surfaces, changed the airflow path and made these prior devices sensitive, unreliable and inconsistent. At the extreme, failure to maintain an adequate seal between the periphery of the housing and the surface being cleaned resulted in inadequate airflow through the housing. In those cases, the cleaning fluid and dislodged debris was not contained under the housing or picked up and removed by the slab cleaner.
Another problem often suffered by those prior devices was ponding of the water on the work surface under the housing. Ponding occurred when the air movement through the housing was insufficient and not directed properly to draw off the cleaning water at the same rate it was being delivered by the spray arm. Water would build up under the housing. Because all of the air being withdrawn from these prior art devices was drawn from under the skirt about the periphery of the housing, a barrier of water up to an inch or more in depth could accumulate on the surface under the housing. Ponding impeded good operation of the device by creating a barrier between the high pressure water stream and the surface to be cleaned. Thus, a portion of the energy of the water stream was dissipated in the standing water, providing little or no cleaning benefit and introducing more turbulence and splashing, making containment more difficult. Further, when operated on uneven surfaces or over the expansion joints of concrete or asphalt slabs, the seal around the perimeter was totally lost, and ponded water and debris was forcefully propelled onto the surrounding surfaces.
The industrial and commercial cleaning industry would benefit greatly from improved slab cleaning apparatus and methods which could overcome the shortcomings discussed above. There has been a long felt but unfulfilled need in the industry for such improved methods and apparatus. The present invention solves that need by correcting the problems described above. The present invention offers a safe method for the precise and controlled removal of hazardous materials as well as other contaminants from industrial and commercial surfaces.